yanmar engine cutting out.

M

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No fuel was getting beyond the injector pump, so had that serviced.

Not cured it though.

It seemed to take a lot to get the air out, then it would run for 1/2 hr hour and stop again. I have only had to bleed it once before and it was quite quick. Could air be being sucked in? The fuel filter was clean.

If it is air being drawn in is there a way of finding it other than replacing all pipes etc one at a time?

Cheers
 
Had similar problems for several years. Took ages to sort out. Here are the things I found. Hope they will give you some more areas to look into.

You mention fuel filter being OK. Is that both of them? I found the one on the engine was clogged up but didn't know it even existed for 3 years (yes, I know, not very observant)

The second issue I had was with one of the unions on the filter by the fuel tank. The copper washer was slightly distorted or had been caught in the thread and this allowed a small amount of air to get in.

Third issue was with the pick up pipe in the tank. Over time, it had curled upwards and wasn't at the bottom of the tank any longer - thus letting in air when heeled

Fourth issue was diesel bug - partially blocked filters and caused intermittent stopping

Good luck!
 
mirror image said:
No fuel was getting beyond the injector pump, so had that serviced.

Not cured it though.

It seemed to take a lot to get the air out, then it would run for 1/2 hr hour and stop again. I have only had to bleed it once before and it was quite quick. Could air be being sucked in? The fuel filter was clean.

If it is air being drawn in is there a way of finding it other than replacing all pipes etc one at a time?

Cheers
Click to expand...

Probably air being sucked in. Mine never cut out until the tank was half-empty - finally found the air-leak was through the on-off tap at the top of the tank. By that time I'd had the tank out, steam-cleaned and re-made nearly every joint in the fuel feed line.
 
I have found that fitting a primer bulb in the suction line is useful: if makes bleeding air and filling the pre-filter much easier and, by pressurising the pipework, if there is a leak it is much easier to spot diesel coming out than air going in.
 
mirror image said:
If it is air being drawn in is there a way of finding it other than replacing all pipes etc one at a time?
Click to expand...

Not sure-fire, but a good start is to clean down everything with solvent and get it dry, then look for and fix *any* weeps of diesel that appear.

Wiping the pipework, etc. down with that purple workshop tissue paper is good for finding leaks as even a small amount of diesel turns it dark.

(I know you're looking for air going it, but diesel is remarkably mobile and will find its way out of small leaks even if not under pressure IMHO.)
 
A blockage in the feed line can sometimes be hard to identify. Either some diesel bug decomposing, or other foreign matter. I've known two examples of silicone getting into a fuel tank..

If the return line is above the feed line, as it often is, then the engine may draw fuel in reverse up the return line, until that comes out of the liquid in the tank, and the engine cuts. This particular problem, in conjunction with the silicone blockage, eluded several engineers and cost us many thousands of pesetas. Foreign matter that will not go up the feed line might block it intermittently, but be drawn back to the honeypot once the engine is restarted.

Blow back down the feed line to check its not blocked. Then pump out, filter and return the fuel to the tank.
 
check your fuel lift pump isn't causing a fault, the none return valves do wear, the lift pump on my 2qm15 is showing signs of this. The engine if left for a week wont start with out a fair amount of cranking, then it starts instantly each and every time
as others have said each and every joint can be at fault

cheers
mick
 
Hmmm! Lots of sensible suggestions to ponder. Due to the intermittent nature of the fault I have confused myself as one minute I had fuel at the injectors and the next it had stopped.

I recall when it first stopped I undid the banjo at the top of the fuel filter, (the line that leads to the injector pump) and I had air bubbles. It started again and ran for a bit. I then managed to convince myself it was the fuel injector pump as was not getting fuel out of it.

I didn't think to check the connections before the fuel filter at the time.

Blue wipes and priming bulb are good ideas.

What would be the symptoms of a faulty lift pump? Is it a case of it works or it doesn't?
 
One of my favorite tricks is to plumb in a piece of clear tubing into the system. Start at the tank end of the fuel system. plumb in the clear tubing. If you see air in the tubing then the leak is down stream of where it is plumbed in. if no leak remove the clear tube. Cut off a small piece of the fuel line that was under the hose clamp and reseal the system. this is b/c the clamp may have caused a hole in the hose big enough for air to come in but not so big for diesel to come out. I always try to leave 6" extra of hose on all my diesel connections. move the clear tube up stream of the primary filter. Keep on moving the clear tubing until you find the leak. Good luck -- it takes a lot of patience but is not rocket science.

If that doesn't work then get some fuel line and plunge it directly into a jerri can of clean diesel and attach the other end to your secondary filter. See if this cause a problem. If not then you can identify that the problem is between the filter, the lift pump, and the fuel tank.
 
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